Computer systems can provide user environment management and/or policy control for computing devices (e.g., Windows-based PCs). A system policy can be defined within an enterprise computer network either: to respond to system events such as computer startup/shutdown, user login/logoff, process start/stop, and session changes, etc.; or to prevent or control user behavior in applications and the desktop environment. For example, a pre-defined script can run when a user logs in to a corporate network; a particular group of users can be prevented from using parts of an application.